Sandwich-type electrochemical immunosensor based on CuFe2O4-Pd for cardiac troponin I detection

A sandwich-type electrochemical immunosensor was designed by highly efficient catalytic cycle amplification strategy of CuFe2O4-Pd for sensitive detection of cardiac troponin I. CuFe2O4 with coupled variable valence metal elements exhibited favorable catalytic performance through bidirectional cycling of Fe2+/Fe3+ and Cu+/Cu2+ redox pairs. More importantly, Cu+ acted as the intermediate product of the catalytic reaction, promoted the regeneration of Fe2+ and ensured the continuous recycling occurrence of the double redox pairs, and significantly amplified the current signal response. Pd nanoparticles (Pd NPs) loaded on the surface of amino-functionalized CuFe2O4 (CuFe2O4-NH2) served as electrochemical mediators to capture labeled antibodies (Ab(2)), and also as co-catalysts of CuFe2O4 to further enhance the catalytic efficiency, thus improving the sensitivity of the electrochemical immunosensor. Under the optimal experimental conditions, the linear range was 0.001 similar to 100 ng/mL, and the detection limit was 1.91 fg/mL. The electrochemical immunosensor has excellent analytical performance, giving a new impetus for the sensitive detection of cTnI.